How to use Blenders GUI?
You may be able to learn the Blender interface while working on your game, but I suspect that this is more of a challenge than you need to take on. If you're totally new to Blender, I think you'll find it salutary to gain some familiarity with the Blender and the Blender interface tools by working through one (or both) of two online courses, one by James Chronsiter at [http://www.cdschools.org/Page/455], with video supplements at [http://4chron.home.comcast.net/~4chron/CDCADTutorials.htm], or alternatively Neil Hirsig's course at [http://gryllus.net/Blender/3D.html]. These will give you a solid introduction to the interface, and some introduction to the BGE.

There are also a number of books available that can help, including free downloads from Wikibooks [http://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro], and a book by John Blain (a bit out of date, but still using basically the same interface as the current edition), [http://download.blender.org/documentation/pdf/John%20M%20Blain%20-%20An%20Introduction%20To%20Blender%203D%20-%20A%20Book%20For%20Beginners%20%282011%29.pdf]